Reports

Early Experiences Accelerate Maturation of the 24-Hour Adrenocortical Rhythm

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Science  14 Mar 1969:
Vol. 163, Issue 3872, pp. 1225-1226
DOI: 10.1126/science.163.3872.1225

Abstract

Rats reared under 12-hour alternating periods of light and dark were killed at times corresponding to the times at which the maximum or minimum plasma corticosterone concentrations occur in mature animals. The characteristic 24-hour adrenocortical rhythm was first observed in rats 21 to 25 days old. In rats handled or stimulated with electric shock, the rhythm developed as early as 16 days.